When Ulrich's mother mentions Claudia Tiedemann (Regina's mother), it is implausible that current day Regina would bear the surname "Tiedemann" since she is married to Aleksander Tiedemann.
When Mr. Tiedemann calls the doctor of his wife about the mammography screening, the doctor's assistant willingly talks about the result of the screening with him. This would never happen due to privacy laws and doctor patient confidentiality.